Semiconductor devices

ABSTRACT

A multijunction, multilayer semiconductor device is formed by alloying the surface of a body of semiconductor material with a material which contains an impurity and includes gaps or perforations therein so that an emitter zone is formed in the body which includes corresponding perforations therein into which project or extend portions of the zone adjacent the emitter zone. The exposed surfaces of the adjacent zones which project into the emitter zone are abraded.

' United States Patent Inventors Clifford Victor Miles;

John M. Garrett, both of London, England Appl. No. 744,660 Filed Patented Assignee Conductors Limited [56] References Cited UNITED STATES PATENTS 2,973,569 3/1961 Feinberg et a1 29/590 X 3,336,160 8/1967 Katz et a1 29/583 X 3,366,851 1/1968 Herlet et al. 29/590 X Primary Examiner-John F. Campbell London, England Assistant ExaminerW. Tupman Priority July 20, 1967 Attorney-Larson, Taylor and Hinds Great Britain ABSTRACT: A multijunction, multilayer semiconductor device is formed by alloying the surface of a body of semicon- SEMICONDUCTOR DEVICES ductor material with a material which contains an impurity 9Claims,3Drawing Figs. and includes gaps or perforations therein so that an emitter U 8 CI 29 590 zone is formed in the body which includes corresponding per- 24/576, rotations therein mm which project or extend portions of the l zone adjacent the emitter zone. The exposed surfaces of the Int. Cl B01 17/00,

H0 7/24 ad acent zones Wl'llCh pro ect Into the emitter zone are Field of Search 29/590, abraded v 8 8 6 I I W 7 [-11 s 1 [/LJV/ P V//[ 4/IJV /IJl //l 7 9 9 Z 8 7 9 7 PATENTEU JAN! 1 [972 Fig. I.

Fig. 2.

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SEMICONDUCTOR DEVICES This invention relates to multizone multijunction semiconductor devices and their method of manufacture.

The present invention provides a method of manufacturing a multizone multijunction semiconductor device in which one of the zones constitutes an emitter zone having therein a perforation into which projects and in which lies a portion of a zone adjacent the emitter zone, which method includes the steps of alloying to a surface of a body of semiconductor material a layer of a first material including an impurity which forms in the emitter zone in the body, the surface of the body being abraded at least where said adjacent zone lies in the perforation in the emitter zone.

Advantageously, the emitter zone has therein a plurality of such perforations, the surface of the body at least where said adjacent zone lies in each of the perforations of the emitter being abraded. The number of perforations may be in excess of 30 and may, conveniently, lie between 30 and 100. Preferably, the perforations are uniformly distributed over the area of said surface of the body and the total area of the perforations may represent between 2.5 and 25 percent of the total area of the surface.

Conveniently, the abrading may be carried out by sandblasting of said adjacent zone at least where it lies in the perforation(s) ofthe emitter zone.

The perforation(s) in the emitter zone may be formed by the layer being a preperforated layer such that when the layer is alloyed to the body, the perforation(s) in the layer forms or form the corresponding perforation(s) in the emitter zone.

The first material may be a gold/antimony alloy.

After the above steps there may be subsequently applied an electrically conductive layer of a second material which layer makes ohmic contact with both said first-mentioned layer and said adjacent zone where it lies in the perforation(s) in the emitter zone so as to electrically interconnect said first-mentioned layer and said adjacent zone.

The present invention also provides a multizone multijunction semiconductor device manufactured by the method described above in any one of the preceding paragraphs.

One embodiment of the present invention will now be described in greater detail by way of example only, with reference to the accompanying drawings wherein FIGS. 1, 2 and 3 are cross-sectional views showing different stages in the production of a semiconductor device according to the invention.

Referring to FIG. 1, body 1 of silicon semiconductor material has formed therein two PN-junctions 2 and 3 extending parallel to two opposed faces 4 and 5 of the body.

As shown in FIG. 2, there is then alloyed to one of these opposed faces 4 an annular-shaped layer 6 of a first material including an impurity which forms in the body 1 of an emitter zone 7, the layer being preperforated (by drilling) with 40 holes 8 each of 0.0l3-inch diameter uniformly distributed over the layer; the holes 8 thus representing approximately 7.5 percent of the total surface area of the layer which had an outside diameter of 0.312 inch and an internal diameter of 0.094 inch, providing an overall area of 0.07 square inch. By the alloying of this layer 6 to the body, there is thus formed in the body the emitter zone 7 which has gaps or perforations 9 therein corresponding one to each of the gaps or perforations 8 in the original layer 6, into which each of which perforations 9 in the emitter zone there projects and therein lies a portion ofa zone 10 adjacent the emitter zone 7.

The material ofthe layer 6 is a gold/antimony alloy.

After the formation of the emitter zone 7 in the above manner, the surface of the portions of the adjacent zone 10 ex tending through the perforations 9 in the emitter zone, are then sandblasted (as at l 1) using a fine powder.

Subsequent to the sandblasting, there is applied (as shown in FIG. 3) by vacuum deposition a second material 12 constituted by successive layers of nickel and gold over both the layer 6 of the first material and the surface of those portions of the zone 10 adjacent the emitter zone which lie in the perforations 9 in the emitter zone 7. During this vacuum deposition,

the remainder of the body of the silicon material is protected from receiving the deposited alloy by a wax coating.

The layer of second material 12 thus ohmically contacts both the layer 6 of the first material and the surface of the portions of the adjacent zone 10 which lie in the perforations 8 in the emitter zone thus electrically to interconnect the emitter zone 7 with the adjacent zone 10.

By virtue of the sandblasting, it has been found that recombination of carriers at the surface of said portions of the adjacent zone occurs, providing a beneficial result, by virtue of an enhanced voltage capability and DV/DT performance of the resultant device.

After the above-described steps, the protective wax coating is removed.

To enhance adhesion of the second material 12, this material is sintered in a hydrogen atmosphere at a temperature not exceeding 450 C.

While in the above-described example, holes 8 of a particular density and of a particular diameter were used, it has been found that alternative densities and diameters are equally satisfactory.

For example, it has been found that with holes of 0.0 l 3-inch diameter, the number may be increased to such that, for the overall sizes above specified, the holes in the layer of the first material would then represent approximately 13 percent of the overall area of the layer. Equally, 48 holes each of 0.018-inch diameter have been used, this representing approximately 17 percent of the layer. Again, 21 holes each of 0.0 l 8- inch diameter have been used which, like the specific example, represents approximately 7.5 percent of the overall area of the layer. Thirty-six holes, each of 0.018-inch diameter, have also been used, this then representing approximately 13 percent of the overall area of the layer. It can be seen, therefore, that the area of the perforations in the layer may represent between 7.5 percent and 17 percent of the overall area of the layer.

Having thus described our invention what we claim is:

l. A method of manufacturing a multizone multijunction semiconductor device including the steps of providing a body of semiconductor material having at one face thereof a first zone of one conductivity type, alloying a layer of conductive material containing an impurity of opposite conductivity type to said face to form an emitter zone in the semiconductor body, the emitter zone so formed including at least one gap within the boundaries thereof which corresponds to a perforation in said layer and into which a portion of said first zone protrudes so as to present an exposed surface area surrounded by said emitter zone, and abrading said exposed surface area surrounded by said emitter zone so as to enhance recombination of carriers in said protruding area of said first zone.

2. A method as claimed in claim 1, wherein the emitter zone has therein a plurality of such gaps, the surface of the body at least where said first zone lies in each of the gaps of the emitter zone being abraded.

3. A method as claimed in claim 2, wherein the number of such gaps is in excess of 30.

4. A method as claimed in claim 3, wherein the number of gaps lies between 30 and 100.

5. A method a claimed in claim 2, wherein the gaps are uniformly distributed over the area of said surface of the body.

6. A method as claimed in claim 2, wherein the total area of the gaps represents between 2.5 and 25 percent of the total area of the surface.

7. A method as claimed in claim 2, wherein the abrading is effected by sandblasting of said first zone where the said first zone lies in the at least one gap of the emitter zone.

8. A method as claimed in claim 1, wherein the at least one gap in the emitter zone is formed by the layer being a preperforated layer such that when the layer is alloyed to the body, the perforation in the layer forms the corresponding gap in the emitter zone.

9. A method as claimed in claim 1, wherein there is subsequently applied an electrically conductive layer of a second material which layer makes ohmic contact with both said firstmentioned layer and said first zone where said first zone lies in the at least one gap in the emitter zone so as electrically interconnect said first-mentioned layer and said first zone. 

2. A method as claimed in claim 1, wherein the emitter zone has therein a plurality of such gaps, the surface of the body at least where said first zone lies in each of the gaps of the emitter zone being abraded.
 3. A method as claimed in claim 2, wherein the number of such gaps is in excess of
 30. 4. A method as claimed in claim 3, wherein the number of gaps lies between 30 and
 100. 5. A method a claimed in claim 2, wherein the gaps are uniformly distributed over the area of said surface of the body.
 6. A method as claimed in claim 2, wherein the total area of the gaps represents between 2.5 and 25 percent of the total area of the surface.
 7. A method as claimed in claim 2, wherein the abrading is effected by sandblasting of said first zone where the said first zone lies in the at least one gap of the emitter zone.
 8. A method as claimed in claim 1, wherein the at least one gap in the emitter zone is formed by the layer being a preperforated layer such that when the layer is alloyed to the body, the perforation in the layer forms the corresponding gap in the emitter zone.
 9. A method as claimed in claim 1, wherein there is subsequently applied an electrically conductive layer of a second material which layer makes ohmic contact with both said first-mentioned layer and said first zone where said first zone lies in the at least one gap in the emitter zone so as electrically interconnect said first-mentioned layer and said first zone. 